Mechanically Robust, Forgeable, and Machinable Cellulose Hydrogel

Tough hydrogels show great promise for flexible electronics, soft robotics, and biomedical applications, but their poor secondary formability limits their practical utility. Here, we developed a one-step regeneration–cross-linking strategy that simultaneously induced regeneration and ionic cross-linking of carboxymethyl cellulose through multivalent metal ions in acidic coagulation baths, producing tough, processable hydrogels. This method overcame key limitations of conventional two-step approaches, including uneven ion diffusion and cross-linking heterogeneity, enabling the fabrication of thick and bulk samples. The resulting Fe³⁺-cross-linked regenerated cellulose hydrogel (RCH-Fe) exhibited a uniform, dense network of sacrificial bonds, delivering exceptional energy dissipation and crack resistance. The optimized RCH-Fe achieved a compressive modulus of ∼9.4 MPa at ∼77.2% strain, while under tension it exhibited a Young’s modulus of ∼16.4 MPa with a strain of ∼61.4%. RCH-Fe maintained its structural integrity during secondary processing (forging/carving). Remarkably, dried RCH-Fe gains enhanced mechanical robustness, enabling jade-like precision sculpting, and demonstrates selective UV-blocking capabilities for optical applications. This work advances tough hydrogels toward high-end customized manufacturing.